Automatic film feed device

ABSTRACT

A plurality of rotatable horizontal turntable disks rotate to feed out or take up motion picture film, as it is transported through a projector. Optional threading arrangements enable any of the turntable disks to function as a supply or take up reel. Moreover, the third turntable effectively provides a spare which gives stand-by reliability. Suitable analog sensors detect film tension or broken film conditions and control the film feed accordingly. The analog sensors eliminate hunting as the mechanical operations proceed.

Potts [451 July 16, 1974 [5 AUTOMATIC FILM FEED DEVICE [76] Inventor: Edwin M. Potts, 710 W. Dodson,

Urbana, 111. 61801 [22] Filed: Nov. 22, 1971 [21] Appl. No.: 200,945

[52] US. Cl. 242/5518, 352/128 [51] Int. Cl B65h 17/48 [58] Field of Search 242/55.18, 55.19 R, 76,

[56] g References Cited UNITED STATES PATENTS 1,132,369 3/1915 Lytton 242/55.l8 2,894,702 7/1959 Heath et a1. 242/76 3,092,764 6/1963 Cooper 318/6 3,244,954 4/1966 Branco 318/7 3,497,158 2/1970 Calaway 242/75.52 X

2/1972 Boudouris et a1 352/92 5/1972 Burth 242/55.19 R

Primary Examiner-Billy S. Taylor Attorney, Agent, or Firm-Alter, Weiss, Whitesel & Laff 5 7] ABSTRACT A plurality of rotatable horizontal turntable disks rotate to feed out or take up motion picture film, as it is transported through a projector. Optional threading arrangements enable any of the turntable disks to function as a supply or take up reel. Moreover, the third turntable effectively provides a spare which gives stand-by reliability. Suitable analog sensors detect film tension or broken film conditions and control the film feed accordingly. The analog sensors eliminate hunting as the mechanical operations proceed.

2 Claims, 20 Drawing Figures PATENTEU JUL 1 s 1924 SHEUIBFS FIGJ PATENTEDJUL 1 s 1914 SHEET 2 0F 5 To PROJECTOR FIG. 26

FROM PROJECTOR V FIG.2F

1 AUTOMATIC FILM FEED DEVICE automatic film feeding means for commercial projectorsused in motion picture theaters.

Commercial motion picture projectors usually have reels which contain approximately twenty minutes of program material. Hence, four to six reels may be used during a feature length motion picture having a show time of one and one-half to two hours. Each reel must be mounted, threaded, and projected. Then, it must be dismounted and rewound.

This conventional projector system is expensive and requires a substantial amount of labor with a high skill level. A number of projectors must be purchased and maintained in good working orderso that the film projection may be switched with no apparent break in the picture at the end of each reel. Finally, the projectionist can become physically exhausted as he runs back and forth between the projectors, rewinding machines and the curtain, lights and music controls, if any problems should occur.

From another viewpoint, many motion picture theaters have been closed because they cannot economically compete with other forms of entertainment and, especially, with free television. If the cost of operating the theater can be reduced, it might restore the motion picture industry to a healthy and profitable condition.

Accordingly, an object of this invention is to provide new and improved automatic film-feeding devices for motion picture projectors. In particular, an object is to provide means for loading a quantity of film equal to a full evenings performance on a device for feeding the film and for automatically taking up the film after it is fed. Here an object is to virtually eliminate all manual attention at the projector, during an evening performance.

Another object of the invention is to eliminate the need for duplicate projectors. Here an object is to operate the projector continuously, and to eliminate the start and stop projector operation, and the wear resulting therefrom.

Still another object of the invention is to reduce the amount of labor required to operate a motion picture theater. Here an object is to provide an automatic theater which may be operated almost entirely from the box office so that one person may perform all labor functions.

In keeping with an aspect of the invention, these and other objects are accomplished by providing a plurality of rotatable horizontal turntable disks which feed out or take up the motion picture film asit is transported through the projector. Optional threading arrangements enable any turntable to function as either a supply or take up reel. Moreover, the third turntable effectively provides a spare which gives standby reliability. Suitable analog sensors detect thefilm tension or broken film conditions and control the tape feed accordingly, without causing mechanical hunting. Also, the method of winding eliminates the need for rewind. Finally, the invention may be coupled to automatic equipment which is programmed to control house lights, curtains or music.

g The nature of a preferred embodiment may be understood best from a study of the attached drawings where:

FIG. 1 is a perspective view of the automatic feed system, a motion picture projector, and a make-up table;

FIGS. 2A-2F schematically show an exemplary filmv travel path as well as indicating alternative paths;

FIG. 3 is a perspective view of a film feed tension sensor at the film feeding point in the center of the turntable;

FIG. 4 is a side elevation view of a film take up tension sensor positioned near the periphery of the turntable;

FIG. 5 is'a perspective view of a mechanical assembly including the film tension sensor controls;

FIG. 6 is a schematic diagram of the sensor circuitry for incorporation in the structure of FIG. 5;

FIG. 7 is a perspective view of a horizontal turntable drive device with a brake mechanism schematically shown in association therewith;

FIG. 8 A-D shows four stop motion, schematic views of the brake and drive sequence used during the film disassembly or tear down operations;

FIG. 9 is a perspective view of a mechanical assembly including a broken film sensor and an end of program sensor; and

FIG. 10 A-B shows two schematic circuit diagrams of the electronic equipment in the sensor of FIG. 9.

The major assemblies of FIG. 1 are a make-up table 50, a projector 51, and an automatic film feed structure 52 vidual discrete reel lengths of film may be spliced together to form a single large unitary roll 54 which lies on any one of three horizontal turntables on the structure 52. Thus, an entire evenings film presentation may be drawn from one of these three turntables and returned to another.

.As the many reels of film are drawn from the makeup table 50, and spliced into a single large unitary film roll 54, a colored adhesive tape is attached to the film at the reel end splice. Later, when the unitary roll 54 is disassembled, cut apart, and reformed into the discrete reel length segments, the colored tape is a visual indication of the end of one reel and the start of the next reel. Thus, a person in control of the make-up table stops the disassembly reeling process when he sees the colored tape leave the unitary roll 54. The film is cut apart at the splice which was made when the discrete film reel lengths of film were joined together. A leader is reattached and a new reel is placed on table 53 to take up the next discrete length of film, as it is pulled from the unitary roll 54. A surface 57 provides work space for making the splices. A control panel 58 provides means whereby the operator may control the make-up or disassembly operations.

The automatic film feed structure 52 comprises a vertical post 60 having a plurality of film feed spools or bobbins 61 on one side and a plurality of horizontal turntable disk support arms 62-64 on the other side. The vertical post 60 is supported on the floor by two leg members 66, 67. Each arm includes an individual motor 70 for driving the individually associated turntable disk in a rotary motion. Preferably, each horizontal turntable disk 70-72, is molded from fiber glass or an equivalent structure. The desired tray characteristics are light weight, strength, and uniform weight distribution so that no balancing is necessary.

To facilitatewinding, each horizontal turntable has a mounting means formed therein, comprising two or more anchor holes 73, 74, adapted to receive a ring 76 which is secured in the anchor holes in place by any attachment means controlled by knobs 77, 78. Before any film is loaded on a horizontal turntable disk, the ring 76 is attached in place. When the film take up winding begins in the automatic film feed structure, the leader is attached to the ring 76. As the film winds around the ring, the unitary roll 54 is formed around the ring 76, which functions as a spool or a bobbin for the made up roll. Then, after the unitary roll of film is assembled, the ring 76 is removed by pulling knobs 77, 78 to release the anchor means from the holes 73, 74. The film is pulled from the center of the unitary roll, during the projection.

During make-up, the discrete reel length of film increments 80 are wound on the turntable disk 71 with the unitary roll 54, beginning near the center of the disk and spreading outwardly so that the film is always taken up onto the outer periphery of the roll. During film projection, the film 81 is then pulled from the center of this unitary roll, and it is fed into the projector 51. The film 82, leaving the projector-51, is taken-up on a second turntable disk 72, much as it is taken-up during the original make-up operation. The number of spools or bobbins 61 enable any of the three turntable disks 70-72 to be used for any of the winding, take-up, or make-up functions.

The inside or outside diameters of the unitary roll 54 change as it receives film or loses film during the winding process. Hence, the turntable disks must rotate at different speeds during the winding process, and each turntable must rotate at its own individual speed.

According to the invention, means are provided for continuously sensing the tape tension and for feeding back an analog signal for controlling the horizontal turntable disk drive, as a function thereof. In greater detail, the film feed path is seen in FIG. 2, which is properly interpreted as a single and unitary, somewhat exploded view which schematiclly shows parts of one optional film path through the film feed assembly. In greater detail, FIG. 2A shows the feed as being taken from turntable disk 71, by way of example; FIG. 2B

shows how the sensor associated with the disk of FIG. 2A detects the presence of the film and the supply nature of the roll; FIG. 2C shows the take up roll as being on turntable 72, by way of example; FIG. 2D shows the sensor associated with the disk of FIG. 2C detects the presenceof the film; FIG. 2E shows a universally usable bobbin for guiding the film over all film paths and between any of the disksand the projector; FIG. 2F perspectively shows the pivot for the bobbin 90 mount; and FIG. shows the array of bobbins in the film feed system. Centrally located within' the unitary roll of film is a combination film feed and tension sensor 85 which is seen in detail in FIG. 3, and a peripherally located tension take up sensor 86 which is seen in detail in FIG.

The film feed members (FIG. 3) comprise a series of bobbins or spools 91-94 which establish a path from the center of the unitary roll on the horizontal film feed 95 to an angularly disposed plane at 96 which lifts and directs the film upwardly and over the inside edge of the film roll 54. From this point, the film follows the path 81 to the spools or bobbins 61, and onto the projector. I

The bobbins are flexibly mounted to conform to a position of least stress upon the film. In greater detail, at least some spool or bobbin mounts comprise a post 87 having an arm 88 pivotally attached thereto at pin 89. Post 87 is secured to vertical post 60 in any suitable manner, and bobbin 90 is freeto pivot on pin 89 between two fixed angular positions responsive to the pull of the tape so that the film may be guided from any source to the bobbins 190. As film feeds over the spool on bobbin 90, the arm 88 swings on pivot 89 to a position of least restraint. This reduces stresses in the film to a minimum.

Means are provided for sensing the feed tension in the film as it is being pulled from the unitary roll 54. In

- greater detail, the film is pulled'at horizontally away from the inside diameter of the unitary roll 54 to pass between posts 97, 98 on a tension sensor arm 99. As the tension increases, arm 99 swings in direction A. As tension decreases, arm 99 swings in direction B. A suitable spring 101 normally urges arm 99 to swing into a normal or home position/As the arm 99 rotates, the shaft 102 turns, and a cam 103 rotates to cut into and selectively reduce a beam of light directed from lamp 104 onto photocell 105. The shape of the cam 103 is such that the amount of light falling on the photocell 105 varies as a function of the shaft 102 position.

a function of the'film feed tension. When no film is present, the cam 103 cuts off all light, the photocell 105 has no output, and the turntable disk stops.

It should now be apparent that, as the film 95 is pulled from the roll '54, the sensor arm 99 swings over arc 106 as the feed'tension changes. Since the cam 103 cuts the light beam falling on cell 105 in a continuously variable manner (i.e. not in incremental discrete steps), there is an analog signal out of cell 105. Hence, the film fed speed may beheld fairly constant. This is as distinguished from a digital control wherein the arm 99 hunts continuously between high and low limits.

From the film feed tension sensor assembly 85 (FIG. 2), the film advances over idler spools or bobbins 61 which direct the film over path 81 to the lens and shuttle assembly of the projector 51. The picture is there projected in the normal and conventional manner. After the projector transports the film past the lens and shuttle assembly in the conventional manner, it discharges the film into path 82. The path for the particular threading of FIG. 2 is shown by solid lines. Optional paths are drawn in dashed lines. There is an alternative path which enables any turntable 70-72to function as either a supply or take up reel.

Means are provided for sensing the tension on the take-up side of the projector. In greater detail, the sensor (FIG. 4) comprises-a pivot arm 110 having a dashpot motion damper 111 associated therewith. Mounted on the end of the pivot arm 110 ar a pair of spools or, bobbins 112 spaced apart for enabling the film 82 to pass betweenthem. As the film tension changes, the pivot arm 110 swings over an are 113 (FIG. 2) to adjust the rotating speed of the take-up turntable disk 72.

' The two sensors 85, 86, are positioned near the axle 114 about which the turntable disk turns. The shaft 102 of the feed tension sensor passes concentrically through a hole in the axle 114, as seen in FIGS. 3 and 5. An adjacent shaft 116 is controlled by the take-up vsensor arm 110, with results which are much the same cast shadows on the photocells 120, 121. The cam 103 rotates under control of the feed tension sensor arm 99, and the cam 103a rotates under the control of the takeup sensor arm 110. Therefore, the amount of light striking photocell 120 is an analog of the feed tension,

and the amount oflight striking the photocell 121 in an analog of the take-up tension.

F l0. 6 is a schematic circuit of the electronic circuits built onto printed circuit cards 124, 125 in the unit 117. In greater detail, commercial sixty cycle 115 volt alternating current is applied across terminals 126, 127. The circuit energized thereby includes feed tension and take-up tension detector photocells 120, 121, respectively, a silicone controlled rectifier (SCR) 130, a diode rectifier bridge 131, an output 132 to the turntable drive motor 70, and various circuit elements 133-141. I I

Since each of these elements is a well known component, it is thought that they will be understood best from a description of how the circuit operates. In greater detail, each of the resistors 133, 137 (in cooperation with capacitor 135) provides a 90 phase shift or a total of a 180 shift of the input AC power wave form, as compared to the voltage applied across SCR 130. r

The device 138 is a bilateral switch which fires when either a positive or a negative signal exceeds more than a certain voltage level. For example, this may be a pair of back to back zener diodes which conduct when the signal on the left (as viewed in FIG. 6) exceeds i 28 volts. The bilateral switch 138 is connected to a gate electrode on the SCR 130. A series circuit including resistor 139 and capacitor 140 by-passes transient voltage spikes to protect the SCR.

A potentiometer 141 may be set to provide a threshold level of operation. In greater detail, the potentiometer 141 is adjusted to a point where less than a trigger current flows to the capacitor 136 whenever the photocells l20, 121 are dark because they are covered by the shadows of cams 103, 103a. Since the film is only able to either feed out or take up at any given time, only one of the cams is operative at any given time. Therefore, only one of the photocells 120, 121 is operative at any given time.

As the cams 103 or 103a rotate to remove their shadows, away from over the photocell 120 or 121, the internal resistance of the exposed photocell goes down. As the resistance goes down, the capacitor 136 charges. Obviously, the time required for the capacitor 136 to charge to a trigger voltage level will vary as a 6 function of the photocells resistance and, therefore, as a function of the cam positions or the film tension.

As graphically drawn at 145, the capacitor 136 charges over a period of time beginning at the zero axis crossings 146, 147 and terminating when a trigger voltage level (such as i 28 volts) is reached at 148, 149. As indicated by the double ended arrows 150, 151, the trigger voltage points 148, 149 may vary as a function of time responsive to the internal photocell resistance. Once the trigger voltage level is reached, the bilateral switch 138 fires, and a gate pulse switches on the SCR 130, which conducts until the voltage reaches the zero crossing points 147, 152, when it switches off. Hence, current flows during the period indicated by cross hatching at 145. More or less current flows depending upon the phase angle of the commercial voltage at the instant when SCR 130 fires and switches on.

Upon reflection, it should now be apparent that bridge 131 supplies a rectified dc. voltage to motor at a level which varies as an analog of film tension. If

ceives less light, the internal resistance goes up, capaci-' tor 136 charges slower, and the SCR fires later. Less current flows through bridge 13] to motor 70, and it slows.

Since the control is an analog signal, the motor tends to hold a steady speed with only minor corrections responsive to changes in film tension. There is no continuous hunting while the motor receives an unending series of speed-up, slow-down command signals.

The turntable diskdrive system is seen in FIG. 7. In greater detail, the lower surface of the turntable disk has a dependent circular drum or flange race integrally formed therein and concentrically located with respect to the axle 114 and outside periphery of the turntable disk. The center of the turntable disk is mounted and rotatable about the turntable axle 114 supported by the individually associated one of the arms 62-64.

Mounted on the arm 63, for example, is a pivot bracket 156 which is held in place by a spring loaded quick disconnect pin controlled by D ring 157. A similar pin (not shown) is provided on the bottom of the bracket 156. Supported on bracket 156 is a motor 70 having a plug-in connector 158 for making electrical connections through arm 63 and vertical member 60 (FIG. 1). If any motor must be repaired, replaced, or exchanged, it is only necessary to pull the electrical plug 158 and the two quick disconnect pins 157. The

bracket 156 lifts or slides off the arm 63. This way, the

the direction of turntable rotation, since the turntable rotates freely as the film is pulled by the turntable 53 during the disassembly of the unitary roll.

According to the invention, a combination of the motor drive assembly mountedon bracket 156 and a brake assembly 165 enables the disk tray to either be driven or to rotate freely, as shown by the four stop motion views of FIG. 8. In greater detail, this assembly includes a motor driven actuator 166, a brake lever arm 167, and a return spring 168. The brake arm is pivoted at 169, and it has a wear resistant pad 170. Under normal operating conditions,-the return spring 168 pulls one end of the lever arm 167, which rotates around the pivot point 169 to lift the other end170 away from the drum 155.

During normal operations, the motor mounting bracket 156 is held snugly against the arm 63 by a bias spring 171. Spring '17] is a coiled or other suitable spring pushing outwardly as viewed in FIG. 7 so that bracket 156 pivots about post 157 to push capstan 159 against drum 155. In this position, the capstan 159 is pressed against the drum 155 to drive the turntable disk 71.

- After the feature run has terminated, it is necessary to make up the original reel size incremental reel length film segments. It is desirable to pull the film off the turntable disk 71 and onto a take-up reel 53 (FIG. '1),

.at a very high rate'of speed. As the splice at the end of pressed tightly against the drum 155 to quickly-stop the rotation.

The meansfor accomplishing this brake-drive operation are seen in FIG. 8. In greater detail, a cable 175 runs from brake arm 167 to a spring 176 and a control arm 177. A motor 178 drives a gear box 179 which controls the arm 177 and causes it to rotate, pulling the cable 175, via spring 176, and thereby swing the brake arm 167 against the drum 155. The motor 178 and gear 179 are any suitable device for urging arm 177 to swing until it encounters a predetermined resistive force and thereafter to slip. The spring 176 absorbs the shock of the mechanical contact between the brake end 170 and the drum 155. When the brake engages the drum 155, it drags the turntable 7.1 to a stop, and the brake actuator motor 178 stalls. However, by selection of a proper motor type, the motor 178 may remain stalled for a relatively long period of time without any damage thereto.

Since the brake is only applied momentarily, the detection of the complete brake on condition poses no problem.

The motor mounting bracket .156 pivots about pin 157 when a solenoid (not shown) adjacent motor 178 is energized. An adjustment bolt 181 limits the amount of travel imparted to the bracket'l56 by this solenoid operation. Thus, as the bracket 156 is pulled in direction C, the capstan 159 swings away in direction D to disengage the drum 155.

The brake-drive operation sequence for returning the unitary roll to the original incremental reel size segments should now be clear. An operator manipulates controls on panel 58. The solenoid is operated to pull this circuit are the lamp 197, photocell 200,

bracket 156 in direction C and swing capstan 159 away from the drum in direction D (FIG. 8B). Also, the spring 168 pulls brake arm 167 away (direction E) from the drum 155. Film is pulled from the turntable disk 71 and onto the reel 53 (FIG. 1) on make-up table 50. The turntable disk 71 rotates freely as the film is so pulled at a very high rate of speed.

When the operator sees a piece of colored tape stuck to'the film, coming off the unitary roll 54, he performs another manual operation at the control panel 58. The end of the brake arm 167 moves (direction F) into contact with the drum 155 (FIG. 8C). The turntable disk 71 stops'turning.

Then the operator cuts the film, removes the rewound reel 53, and starts rewinding a new reel. Then, he performs another manual operation at the control panel 58 to again place the system in the condition of FIG- 8B. The process is repeated each time that a reel length segment of film is removed from the unitary roll.

After the last segment is removed, a manual operation at the control panel 58 returns the brake and motor driven capstan to their original state (FIG. 8D).

Sensor means are provided for detecting broken or stalled film. In greater detail, the film path 82 (FIG. 2) leads from the projector directly to a pair of spools or bobbins through which the film 191 passes (FIG.

9). The film has the conventional and well known rows of sprocket holes 192, 193 running along each edge thereof. The movement of these sprocket holes actsas a light chopper for giving a continuous flow of pulses, thereby indicating movement of the film. r

A post 198 (FIG. 9) is rigidly affixed to the vertical member 60 near the bobbins 190. A shaft 196 is pivotally attached at 194 to the outer end of post 198. The shaftl96 supports a box 195 containing an electronic sensor circuit shown in FIG. 10. This structure is mounted ona post approximately the same as the bobbin post seen at 87-90 in FIG. 2. Hence, the sensor may freely swing to a proper position with respect to the film, where it is locked in place. The sensoralso includes an arm supporting a lamp 197 positioned in front of the row of sprocket holes 192 and shining through the sprocket holes onto a photocell 200 (FIG. 10B) in the end of the box 195. As long as the film continues to feed, the sprocket holes chop the light beam, and the sensor enables the system to operate. If the film stops or breaks,.the chopping stops and the film feed is cut off. The sensor then gives an inhibit signal to stop the system operation.

The sensor circuit for accomplishing the broken film detection is seen in FIG. 10A. The major divisions of an amplifier 201, and a relay 202 driven by a transistor 203. The lamp 197 is lit from a +18 volt battery 210, at an illumination level set by an adjustment of a potentiometer 211. A'coupling and current limiting resistor 212 connects the battery 210 to the photocell 200 via a load resistor 213 and a voltage regulating zener diode 214.

The photocell 200 conducts each time that light passes from the lamp 197 through a sprocket hole 192 to the photocell 200. Hence, the photocell-200 generates a series of pulses as long as the light chopping action of the sprocket holes continues.

The collector of photocell 200 is connected to the input of amplifier 201, via a capacitor 220, and a gain adjusting resistor 221. Resistor 222 also helps set the gain. The capacitor 220 passes the pulses generated by' ther of the turntable disks 70 or 71.

the photocell 2 responsive to the light chopping action of the sprocket holes, but blocks the dc. bias. Hence, the amplifier 201 receives a signal only while the film is running.

V dc. signal. Amplifier 201 switches off, and relay 202 releases. If there should be apower failure, relay 202 also releases. Either way contacts 236 open to inhibit further operation.

Means are provided for initiating an intermission sequence responsive to the completion of a predetermined amount of feature presentation: In greater detail, a short length of ferrous tape 230 (FIG. B) is stuck on the film 191 at the point in the program where an intermission sequence is desired. The sensor 195 includes a pick up coil 231 in which a pulse is induced when the ferrous tape passes thereby, (i.e., the ferrous tape isa moving armature relative-to the coil and therefore it changes the coils reluctance). The pulse is fed through an amplifier 232- to operatea'relay 233 and pulse a set of contacts 234. The FIG. 10B circuitry associated with the amplifier 232 is essentially thesame as the FIG; 10A circuitry associated with the amplifier 201 in FIG. 10A.

When the contact, 234 pulse, other control equipment (not shown) operates through a programmed sequence involving a raising and lowering of the house lights, opening andclosing of the curtains, and a playing recorded music.

From the foregoing, it should be apparent that the invention provides means for automating the entire film presentation. One person may operate the box office, sell tickets, and admit patrons to the theater. When the show is to begin, a switch is operated in the box office, and the entire evenings performance is provided by drawing a single unitary roll on turntable disk 71 and depositing it on disk 72. After an appropriate amount of film is drawn, the intermission occurs automatically; then, the film resumes after a timed intermission. After the entire program is finished, the person in the box office may go home almost as soon as the last patron leaves. There is no need to rewind the film. The next night, the film will be pulled from turntable disk 72 and fed over a different path through the projector 51 to ei- Those who are skilled in the art will readily perceive various changes and modifications which will fall within the scope and spirit of the invention. For exam- I 10 the film feed is thereby switched off. A similar spring (not-shown) is inside the structure 111 to hold the cam 103a in a position which switches off the take up. An

advantage of this arrangement is that the device automatically feeds, takes up, etc. according to the program set up when the film is originally threaded. There is no need for human programming of feed, take up, etc. by operating switches, making punched cards, or the like. On the other hand, by the simple expedient of placing the potentiometer 141 (FIG. 6) on the take up table 50, it is possible to-override the automatic speed control circuit of FIG. 6 and to run the turntables at any desired speed. In the electronic circuits, certain components are shown and described. For some of these, there are preferred characteristics. For example, the photocells 120, 121 (FIG. 5) are preferably variable resistive devices since they operate bilaterally with either polarity, as shown in FIG. 6. On the other hand, the photocell 200 (FIG. 10A) is preferably a photo- Darlington transistor because it has high gain and a narrow acceptance beam, in the order of three degrees.

Other advantages and modifications will occur to.

those who are skilled in the art. Therefore, the appended claims are to be construed to cover all equivalent structures falling within the scope and spirit of the invention.

I claim:

1. An automatic film feed device comprisinga plurality of rotatable turntable disks which rotate to feed out or take up a rool of motion picture fi'lm' as it is transported through a motion picture projector,

means for providing a plurality of optional film threading paths which enable any of the turntable disks to function as either a supply or a take up reel withoutrequiring rewinding,

means for causing said film to travel from the feed out roll to. the take up roll,

at least one analog sensor means individually associated with each of the turntable disks for automatically detecting-film tension at the associated turntable disks and for controlling the rate at which the associated turntable disks rotate to feed or take up the film responsive to the path selected when the film is threaded through the projector,

means as for-sensing film movement through said film feed device,

' means responsive to said sensor detecting a termination of said film movement for stopping said'film travel,

said means for sensing film movement comprises means for projecting alight beam through sprokect holes in said film, whereby said film movement chops said light beam,

means responsive to said chopped light beam for generating a corresponding train of electrical control pulses, and pulse responsive means for enabling said film feed means as long as said train of control pulses continue. e 2. An automatic film feed device comprising a plurality of rotatable tumtabledisks which rotate to feed out or take up a roll of motion picture film as it is transported through a motion picture projector,

means for providing a plurality of optional film threading paths which enable any of the turntable disks to function as either a supply or a take up reel without requiring rewinding,

means for causing said film to travel from the feed out rool to the take up roll, at least one analog sensor means individually associated with each of the turntable disks for automatically detecting film tension at the associated turntable disks and for controlling the rate at which the associated turntable disk rotates to feed out or take up the film responsive to the path selected when the film is threaded through the projector,

' each of the turntable disks has an upper side and a lower side, said lower side having a drum-shaped race formed freely, or to be stopped. 

1. An automatic film feed device comprising a plurality of rotatable turntable disks which rotate to feed out or take up a rool of motion picture film as it is transported through a motion picture projector, means for providing a plurality of optional film threading paths which enable any of the turntable disks to function as either a supply or a take up reel without requiring rewinding, means for causing said film to travel from the feed out roll to the take up roll, at least one analog sensor means individually associated with each of the turntable disks for automatically detecting film tension at the associated turntable disks and for controlling the rate at which the associated turntable disks rotate to feed or take up the film responsive to the path selected when the film is threaded through the projector, means as for sensing film movement through said film feed device, means responsive to said sensor detecting a termination of said film movement for stopping said film travel, said means for sensing film movement comprises means for projecting a light beam through sprokect holes in said film, whereby said film movement chops said light beam, means responsive to said chopped light beam for generating a corresponding train of electrical control pulses, and pulse responsive means for enabling said film feed means as long as said train of control pulses continue.
 2. An automatic film feed device comprising a plurality of rotatable turntable disks which rotate to feed out or take up a roll of motion picture film as it is transported through a motion picture projector, means for providing a plurality of optional film threading paths which enable any of the turntable disks to function as either a supply or a take up reel without requiring rewinding, means for causing said film to travel from the feed out rool to the take up roll, at least one analog sensor means individually associated with each of the turntable disks for automatically detecting film tension at the associated turntable disks and for controlling the rate at which the associated turntable disk rotates to feed out or take up the film responsive to the path selected when the film is threaded through the projector, each of the turntable disks has an upper side and a lower side, said lower side having a drum-shaped race formed thereon, drive means individually associated with each of said turntable disks, said drive means comprising a motor driven capstan running on sAid race, at least one of said turntable disks having an associated brake means, and means for selectively moving said capstan and said brake against and away from said race for selectively enabling said turntable to be driven, to rotate freely, or to be stopped. 